Today's world economy is mainly based on fossil energy, such as coal, oil and natural gas. However, these non-renewable fossil energy are becoming exhausted. Since the beginning of the 21st century, global energy issues, the consequent environmental pollution and global warming become increasingly apparent and intense. Solar energy has numerous advantages such as the broad and widespread distribution, large resource quantity, no pollution, clean, safety and convenient access, therefore it is considered to be one of the most promising renewable sources of energy.
To take full advantage of the solar energy radiated from the sun, people continue to develop new materials to absorb sunlight, in which inorganic semiconductor materials, such as silicon cells used on the ground, has gained broader development and application. However, due to their complex process and high cost, the application of the silicon cells has been strictly limited. In order to reduce costs and expand the application scope, people have been looking for new alternative semiconductor materials for a long period of time.
In recent years, organic materials have gradually gained widespread interest. For example, after the report of photo-induced electron transfer phenomena between conjugated polymers and C60 by N. S. Sariciftci in 1992, people have put lots of research on conjugated polymer used in the solar cell, and have achieved rapid development. Solar cells directly transform solar energy into electric energy, which is an effective method of using solar energy.
Organic solar cell is a new type of solar cell. Compared with the disadvantages of the inorganic semiconductor materials such as limited sources, high prices, toxicity, complicated preparation process, high cost, the organic solar cell has some advantages such as wide range of materials, structural diversity and manageability, low cost, safety and environmental protection, simple production process, light weight of product, flexible preparation for large area, etc., thus it has important developing and applicable prospects and can be widely used in the fields of architecture, illumination and power generation. However, photoelectric conversion efficiency of organic solar cells is much lower than that of inorganic solar cells for now. Therefore, the development of new organic materials is of great significance for improving the efficiencies of organic solar cells and other semiconductor devices or optoelectronic devices.